Birds and bats enhance yields in Afrotropical cacao agroforests only
under high shade
Sub-Saharan Africa produces most of the Earth’s cacao. Although pests
cause losses of hundreds of millions annually, the role of cacao pest
suppressors remains unknown. We used an exclusion experiment to prevent
access of bats and birds to cacao trees and quantified how their absence
affected arthropod communities, herbivory, and crop yield. Overall,
Mealybugs and other hemipteran pests were more abundant in exclosures.
Under heavy shade (90%), cacao trees with vertebrate exclosures had 3.9
times fewer flowers and 3.2 times fewer large pods than control trees,
corresponding to losses on average of $478 ha-1y-1. Under low shade
cover (10%) however, the opposite pattern was evident: exclosures trees
had 5.2 times more flowers and 3.7 times more large pods than control
trees, corresponding to savings on average of $796 ha-1y-1. Our study
demonstrates that the enormous potential of African bats and birds as
pest suppressors is dependent on shade tree management.